Known have been a DC-to-DC converter, an inverter, and the like as power conversion devices (power modules) that generate driving power for electric vehicles (EVs) or hybrid electric vehicles (HEVs). In these power conversion devices, a large driving current flows to a semiconductor module including a semiconductor element such as an insulated gate bipolar transistor (IGBT) at the time of driving in some cases. That is, it is important to cool the semiconductor module at the time of driving and suppress heat generation.
Conventionally, in order to suppress heat generation of the semiconductor module, the following cooling configuration (see Patent Literature 1, for example) has been known. In the cooling configuration, the semiconductor module and a cooling member are alternately stacked. Then, the semiconductor module and the cooling member are pressurized by a pressure unit formed by a disc spring from one side in the stacking direction thereof so as to hold them close together, and are cooled. The disc spring has a deflection region on which load is nearly constant so as to absorb the difference in dimension due to manufacturing variations (dimensional tolerances in the stacking direction) of the power conversion device (see Patent Literature 2, for example).